1. Field of the Invention
The present invention relates to a camera control system and a camera control method suited for use in a surveillance camera, a video conference system or the like arranged to communicate information, for example, through a network.
2. Description of Related Art
Control systems have heretofore been developed for controlling the image pickup module of a camera, such as control over zooming, focusing and exposure actions of the camera, from a computer or the like via a communication medium, such as RS-232C or the like. Meanwhile, there has been proposed a camera control system in which to such a computer (hereinafter referred to as a camera server) is connected via a network an external control terminal for causing the camera server to execute a command for control over the image pickup module of the camera.
In the conventional camera control system, however, the camera server has been unable to smoothly control the zooming of the camera to obtain a desired zoom magnification, because of a delay of transmission of information due to a length of time required for communication by the RS-232C or a network, or the like.
This problem results from the zooming control arrangement of the camera including instructions only for moving and stopping a zoom lens and reading a pulse value of a zoom motor (or a stepping motor) in response to commands from the control terminal (or the camera server). The camera is not arranged to give any internal command for directly setting a pulse value of the zoom lens on the basis of a command coming from outside, i.e., from the control terminal or the camera server and for moving the zoom lens to a position corresponding to the set pulse value. Incidentally, in many cases, the zoom lens is arranged to be driven by a motor and the position of the zoom lens is controlled by using a pulse value of the motor, which is a value indicating the position of the zoom lens determined with a position corresponding to a zero pulse value of the motor used as a reference position.
More specifically, in a case where the zoom magnification of the camera is to be controlled to a desired magnification only by sending instructions from the camera server to the camera for moving and stopping a zoom lens and reading pulse values, the position of the zoom lens is read after the zoom lens is moved and information on the position of the zoom lens is sent to the camera server. The camera server then determines arrival of the zoom lens at a desired (or target) position and sends an instruction to the camera to stop moving the zoom lens according to the information on the zoom lens position received.
In the case of such a system, however, when the stopping instruction is sent to the camera with the target position determined to have been attained, the zoom action cannot be brought to a stop exactly where a desired zoom magnification is attained, because of a time lag which results from a communication delay over the network or the reaction (response) time of an image pickup module. Under such a condition, the zoom lens would be brought to a stop at a position deviating from a target pulse position.
The invention is directed to the solution of the problem of the prior art described above. It is, therefore, an object of the invention to provide a camera control system which is capable of accurately controlling a camera to obtain a desired zoom magnification even with the simple construction of the camera.
To attain the above object, in accordance with an aspect of the invention, there is provided a camera control device for remotely controlling a camera having a zoom lens capable of varying a magnification thereof by varying a position thereof in an optical axis direction, which comprises issuing means for issuing a designated magnification of the zoom lens, recognition means for recognizing a relation between a position of the zoom lens based on the designated magnification of the zoom lens issued by the issuing means and a current position of the zoom lens, calculating means for calculating a transmission time required for transmission of information between the camera and the camera control device, and forming means for forming a control command for the zoom lens on the basis of the relation recognized by the recognition means between the position of the zoom lens based on the designated magnification of the zoom lens issued by the issuing means and the current position of the zoom lens and the transmission time calculated by the calculating means.
To attain the above object, in accordance with another aspect of the invention, there is provided a camera control system in which a camera connected to a camera server is controllable by a camera control device via a network, wherein the camera comprises a zoom lens capable of varying a magnification thereof by varying a position thereof in an optical axis direction, the camera control device comprises issuing means for issuing a designated magnification of the zoom lens, recognition means for recognizing a relation between a position of the zoom lens based on the designated magnification of the zoom lens issued by the issuing means and a current position of the zoom lens, calculating means for calculating a transmission time required for transmission of information between the camera and the camera control device, and forming means for forming a control command for the zoom lens on the basis of the relation recognized by the recognition means between the position of the zoom lens based on the designated magnification of the zoom lens issued by the issuing means and the current position of the zoom lens and the transmission time calculated by the calculating means, and the camera server comprises detection means for detecting the current position of the zoom lens, and transmission means for transmitting to the camera control device information on the current position of the zoom lens detected by the detection means.
To attain the above object, in accordance with a further aspect of the invention, there is provided a storage medium in which a control program is stored for controlling a camera control device which remotely controls a camera having a zoom lens capable of varying a magnification thereof by varying a position thereof in an optical axis direction, the control program causing the camera control device to issue a designated magnification of the zoom lens, to recognize a relation between a position of the zoom lens based on the designated magnification of the zoom lens issued and a current position of the zoom lens, to calculate a transmission time required for transmission of information between the camera and the camera control device, and to form a control command for the zoom lens on the basis of the relation between the position of the zoom lens based on the designated magnification of the zoom lens issued and the current position of the zoom lens and the transmission time calculated.
To attain the above object, in accordance with a still further aspect of the invention, there is provided a control method for a camera control device which remotely controls a camera having a zoom lens capable of varying a magnification thereof by varying a position thereof in an optical axis direction, the control method comprising an issuing step of issuing a designated magnification of the zoom lens, a recognition step of recognizing a relation between a position of the zoom lens based on the designated magnification of the zoom lens issued by the issuing step and a current position of the zoom lens, a calculating step of calculating a transmission time required for transmission of information between the camera and the camera control device, and a forming step of forming a control command for the zoom lens on the basis of the relation recognized by the recognition step between the position of the zoom lens based on the designated magnification of the zoom lens issued by the issuing step and the current position of the zoom lens and the transmission time calculated by the calculating step.
The above and other objects and features of the invention will become apparent from the following detailed description of embodiments thereof taken in connection with the accompanying drawings.